An original SF talent has now turned to humorous fantasy. In the Kingdom of Underhill, the toddler Prince Amatus sips the Wine of the Gods--and his left side vanishes. The King orders the execution of the four royal attendants deemed responsible for the calamity, eventually replacing them with Companions who join Amatus on a series of deadly quests. As the Companions fall one by one, Amatus rises to the stature of a hero-king, regaining his left side and throne along the way. Barnes fills the narrative with the intelligent world-building, well-chosen detail, smooth prose and deft characterization that have marked his other books (including Mother of Storms, nominated for a 1995 Hugo Award). It is also permeated with verbal wit--men are deadly shots with pismires, and the Vulgarians are housed in stupors--but the wordplay palls deeper into the story, as sympathetic characters die by the handful and Underhill comes to resemble Bosnia. While not completely successful either as straight high fantasy or as a satire of the genre, however, the novel still manages to generate a great sense of fun. (Apr.)